Non-suicidal self-injury (NSSI) refers to the intentional injuring of one's body tissue without suicidal intent and for purposes not socially sanctioned. Examples include skin-cutting, burning, and scratching. NSSI is a robust risk-factor for psychiatric disorders and suicide and has become a significant public health problem in adolescents. Recent research finds that approximately 8% of middle school students, 14-15% of high-school students, and 80% of adolescent inpatients have engaged in NSSI. Because most NSSI research has focused on prevalence and psychosocial correlates, little is known about the functions of NSSI in adolescents. Understanding the functions of NSSI would facilitate case conceptualization and treatment planning for patients who self-injure, and provide a meaningful context for research on the etiology, classification, prevention, and treatment of NSSI. The specific aims are to: 1) determine the suitability of a new, comprehensive measure of NSSI functions for adolescent populations, 2) establish the factor structure of NSSI functions in adolescents, and 3) examine the implications of different NSSI functions for diagnosis and treatment, including the identification of clinically distinct subgroups of self-injurers. Thus, the study will provide basic data on the covariation and clinical implications of NSSI functions, as well as produce the first comprehensive and valid measure of NSSI functions. PUBLIC HEALTH RELEVANCE: Non-suicidal self-injury (NSSI) is a robust risk-factor for psychiatric disorders and suicide and has become a significant public health problem in adolescents. Because most NSSI research has focused on prevalence and psychosocial correlates, the present project focuses on the functions of adolescent NSSI, including their measurement, structure, and clinical implications.